The present invention relates to a printing method of electronic document data while preventing their forgery or copy.
More particularly, the present invention relates to a forgery preventing technique which prevents the printed matters from being copied in a currently spread printer.
The related art of the present invention is exemplified by Japanese Patent Laid-open Publication No. 2003-136828 (hereinafter, referred to as Patent Document 1) and Japanese Patent Laid-open Publication No. 2002-366981 (hereinafter, referred to as Patent Document 2).
In the invention described in Patent Document 1, one continuous gradation image can be printed in a predetermined area. At the same time, two continuous gradation images can be arranged equally in a predetermined area with neither any superimposition on a predetermined area nor any fusion of the mesh points. As a result, security prints which prevent forgery or alteration of the printed matters can be realized at a low cost with the four colors of cyan, magenta, yellow and black, which are widely used in the general market.
Of the four basic colors of the cyan (C), magenta (M), yellow (Y) and black (Bk) used generally in the commercial prints, more specifically, the black (Bk) is a black pigment composed mainly of carbon black, and exhibits an absorption over the whole range from an ultraviolet range to an infrared range. By making use of the fact that the superimposition of the other cyan (C), magenta (M) and yellow (Y) does not absorb the infrared ray, the image printed in the black ink (Bk) containing carbon black can be visually recognized by the observation using a survey device such as an infrared camera which observes the absorptivity of the infrared ray.
According to the invention described in Patent Document 2, a ticket issuing system having a high effect to prevent the counterfeit tickets from being printed by the forgery or copy can be provided merely by installing the ticket image encoding print programs provided by the ticket issuing center and by using the currently spread system of the terminal and the printer connected with the internet.